Grouping does not work out of the box

I'm using a KryptonOutlookGrid in a Winforms app. Columns and rows have been constructed like mentioned in the Getting Started Article. When the user tries to drag a column header to the GroupBox, no column header can be dragged to the drop box.

When I right click the 5-th column header and click on group by this column in the context menu, grouping is always done by the first column. Grouping by code seems to work.